The complexity of the messenger RNA (mRNA) population in various anatomical regions of the mouse brain will be measured. Transcriptional diversity and overlap of glial and neuronal nuclear RNA's will be determined. The relationship between nuclear polyA and polysomal polyA RNA will be explored. Nuclear RNA populations will be studied in terms of polyA plus and polyA minus unique sequence transcripts. The basic methodologies to be used include: DNA/RNA hybridization using unique sequence DNA and various "population probe" fractions of this DNA, various affinity chromatographic procedures, centrifugation in denaturing gradients, electromicroscopy, counterflow centrifugation for nuclear fractionation, S'nuclease coupled with hydroxyapatite chromatography in hybridization assays, and a variety of other minor techniques such as alkali cleavage and biochemical assays for characterizing nucleic acids.